I hate to break this to you, but unless you have found some sort of magical pump, it's gonna run on 12v too. Plus it's probably gonna suck more than a 12v furnace fan and could possibly be noisier. I have a small Suburban gas furnace with a 12v fan in my Lance camper. I run it all night at 68 degrees usually and have no problem starting my truck the next day. If you need more 12v reserve, just add batteries, they're cheap. I have the 2 from my PSD and the one from the camper all tied together so I have 3 to draw from. I can usually run my evap cooler or furnace plus all the lights, water pump, etc.. from the time I park Friday 'til the time I leave Sunday and the truck will still start. If my battery monitor drops to yellow, I can always start the Ford for fifteen minutes to charge them back up, it's got a big alternator that charges it up fast. IMO, you're making it too hard. Just get a furnace and extra batteries if you fall short on reserve power. If you have a generator, you can alway charge the batteries off it too. I don't even have a generator on my camper, and have never really needed it. All of my appliances are gas or 12v, the microwave if I use it runs off a 12v inverter.